Pneumatic tool construction

ABSTRACT

A housing of a pneumatic tool has a curved portion provided with outlet openings for spent pneumatic fluid. An auxiliary muffler is provided for the tool, including a curved body which is dimensioned to embrace the curved portion of the housing and provided with one or more channels overlying the outlet openings and having an end portion provided with discharge apertures. The channel or channels follow substantially the curvature of the curved portion and have a length corresponding to at least half the length of the curvature of the curved portion.

Umted States Patent 11 1 1111 3,891,049 Stroezel et al. June 24, 1975 PNEUMATIC TOOL CONSTRUCTION 3,365,022 1/1968 Barber et a1. 181/36 R 3,379,278 4/1968 Skowron 181/36 R [75] lnvemorsl stmelelz 4 3,459,275 8/1969 Prillwitz et a]. 181/36 R Lemfelden-oberalchen; Alfred 3,635,299 1/1972 Hayes 181/36 A t ic te en; Alfredo Civarella, 3,662,855 5/1972 Adams 181/33 A L f ld 11 f6 em e a O elmany FOREIGN PATENTS OR APPLICATIONS [73] Asslgnee Robe" Stuttgart 43,968 12/1961 Germany 181/36 R Germany 351,921 1/1958 Switzerland 181/36 R 22 Filed: Aug 24 973 951,805 3/1964 United Kingdom 181/36 A [211 APP! N09 391,289 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Wt. W. Miska [30] Foreign Application priority D Attorney, Agent or Firm-Michael S. Striker Sept. 28. 1972 Germany 72-35753[U] [57] ABSTRACT 52 US. (:1. 181/36 A; 181/57 A housing f pneumatic tool has a curved portion [51] Int. Cl. F011 l/08 id d i h/outl t openings for spent pneumatic 1 Field of Search 181/36 A! 36 R, 35 42, fluid. An auxili'a lry muffler is provided for the tool. in-

181/49, 72 eluding a curved body which is dimensioned to em- 1 brace the curved portion of the housing and provided 1 Referellces Cited with one or more channels overlying the outlet open- UNITED STATES PATENTS ings and having an end portion provided with dis- 2.128 742 8/1938 Fuehrer 181/36 A Charge apertures The Channel or Channels follow 2.815088 12/1957 Gibel 181/36 A tan ially he curvature of the curved portion and have 2.949.975 8/1960 Plummer 181/36 A a length corresponding to at least half the length of 3,202,239 8/1965 Clarke 181/36 R the curvature of the curved portion, 3,225,861 12/1965 Reynolds 181/36 R 3.263.770 8/1966 Alm 181/36 R 5 ClalmS, 4 Drawmg Flgures 1- i 7 O O O M 8 3 3 888 O O O 88 8- 2 888 PATENTEDJUN 24 I975 SHEET NN O 000000000 0 000000000 000000000 .1 II. J J HHU ON a Q 0000000900 O0 000 00000 oooooooboo PATENTEDJUN24 I975 89 1, 049

' sum 2 1 PNEUMATIC TOOL CONSTRUCTION BACKGROUND OF THE INVENTION The present invention relates to a pneumatic tool construction in general, and more particularly to an auxiliary muffler for use with pneumatic tools.

It is known to provide pneumatic tools, for instance grinding tools or the like, with outlet openings in the housing, through which openings the spent pneumatic fluid is vented to the exterior. Because this fluid is not entirely depressurized within the tool itself, it exits through the outlet openings with a substantial amount of noise into the ambient atmosphere where it yields up its residual energy and becomes fully depressurized. The amount of noise is so significant that it is found to be a substantial burden upon the user of such a tool, and that it may even have deleterious influences upon his health.

It has also been found that the not yet completely depressurized fluid which is vented through these outlet openings often blows against the body of a user, in some instances even into his face. This is also found to be highly disturbing. For instance, in many tools of this type the outlet openings are provided at the right-hand side of the tool where they are particularly objectionable for the left-handed user, and vice versa.

SUMMARY OF THE INVENTION It isan object of the invention to overcome the disadvantages of the prior art.

More particularly, it is an object of the invention to provide an improved pneumatic tool construction wherein the spent fluid issuing through the outlet openings in the tool housing can become fully depressurized before it vents into the ambient atmosphere.

Another object of the invention is to provide such a construction wherein an auxiliary muffler is provided which not only assures that the spent fluid will become fully depressurized before it enters into the ambient atmosphere, but which also will muffle the objectionable noises.

An additional object of the invention is to provide such an auxiliary muffle which guides the exiting spent fluid in a desired direction.

In keeping with these objects, and others which will become apparent hereafter, one feature of the invention resides, in a pneumatic tool, in a combination which briefly stated comprises a housing having a curved portion provided with outlet openings for spent pneumatic fluid, and an auxiliary muffler for the tool. The muffler includes a curved body dimensioned to embrace the curved portion and being provided with at least one channel overlying at least some of the openings and having an end portion provided with discharge apertures. The channel substantially follows the curvature of the curved portion and has a length which corresponds with at least half the length of the curvature of the curved portion.

It has been found to be particularly advantageous if the channel is formed as a groove-shaped recess in an inner surface of the muffler which faces the outer surface of the housing wherein the outlet openings are provided. The muffler may have a strip-shaped portion which is arcuately curved and on the inner surface of which there is mounted a strip-like formed or shaped component of soft or foam material, particularly rubher, that is a material which is resiliently displaceable. This component is bonded or otherwise secured to this inner surface and defines the lateral walls of the channel.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a manually held grinding machine of pneumatic type, provided with an auxiliary muffler according to the present invention;

FIG. 2 is a section taken on line II-II of FIG. 1, on a somewhat enlarged scale and in diagrammatic form;

FIG. 3 is a developed view of the interior of the muffler; and

FIG. 4 is a view similar to FIG. 3 but illustrating an additional embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing in detail, and referring firstly to the embodiment illustrated in FIGS. 1-3, it will be seen that FIG. 1 shows a pneumatically operated manually held grinding machine. The particular construction and operation of such pneumatic tools if of no consequence here, because such tools are well known to those skilled in the art and the particular construction of the tool itself forms no part of the invention. The tool has a housing portion I accommodating a drive motor 8 which is shown only diagrammatically and which is a pneumatic drive for driving the tool. A front housing portion 2 is provided, from which a grinding spindle 3 extends which is provided at its free end with a mounting device 4 for mounting a non-illustrated grinding disk.

The rear end of the housing, that is the end remote from the spindle 3, is configurated as a hand grip portion 5 having a connecting nipple 6 for a non-illustrated conduit through which pneumatic fluid is to be supplied to the motor 8. A switch or lever 7 is provided on the hand grip portion 5, for the purpose of opening or closing a valve accommodated in the portion 5 (but not shown) which controls the supply of pneumatic fluid from the nipple 6 to the motor 8.

Adjacent the end of the housing portion 1 which merges into the housing portion 2, the housing portion 1 is provided with a plurality of outlet openings 9 through which the spent pneumatic fluid issuing from the motor 8 can vent into the ambient atmosphere. In the illustrated embodiment the openings 9 are arranged in form of three parallel rows each having 10 of the outlet openings. The housing portion 1 is arcuately curved where the openings 9 are provided.

An auxiliary muffler 10 is provided, straddling the housing portion 1 over the surface area thereof which is provided with the outlet openings 9. It has an arcuately curved sheet metal strip 11 which is held in the position illustrated in FIG. 2 by having two end portions 12 bent at an angle and having one or more screws 13 (only one shown) extend through the portions 12, or rather through openings provided in them.

The inner surface of the strip which faces the outer surface of the housing portion 1 is provided in the illustrated embodiment with two parallel air channels 14, which are separated from one another by a divider wall 16. Approximately midway intermediate the opposite ends of the wall 16 the latter is provided with an opening 17 through which the two channels 14 and 15 communicate with one another. The channels 14 and 15 are formed in that the inner surface of the strip 11 has bonded or otherwise secured to it a strip-like shaped component 18 which in the illustrated embodiment is of soft rubber but could be of synthetic plastic material or the like. The channels 14 and 15 are formed in form of recesses or grooves in the component 18. The open sides of the channels 14 and 15 face toward and are covered by the outer surface of the housing portion 1, when the muffler 10 is in the position illustrated in FIG. 2. Thus, the channels 14 and 15 are completely closed at all sides. The developed length of the channels corresponds in the illustrated embodiment to approximately 75% of the circumferential length of the housing portion 1 where the same is embraced or straddled by the muffler 10, as shown in FIG. 2.

The muffler 10 is so connected with the housing portion 1 that one end of the channel 15 overlies the openings 9 which are illustrated in form of the chain-like boxes 9 in FIGS. 1 and 3. The other end of the channel 14, which extends in parallelism with the channel 15, is provided with discharge openings 19 which are formed in the strip 11. In their size, arrangement and number the openings 19 correspond to the openings 9. In other words, in the illustrated embodiment, an airflow path 20 which is shown in chain lines in FIG. 3 is thus obtained. This is a relatively long path for the air to traverse as it passes through the channels 15 and 14, so that the air exiting through the outlet openings 9 can become completely depressurized before it is finally vented to the ambient atmosphere through the openings 19.-

Tests which I have conducted have shown that even if the tool operates at maximum capacity, the use of the muffler 10 permits a very significant reduction in the noise level of the operation of the tool but causes only a very small decrease in its effectiveness.

Due to the fact the the component 18 is of soft rubber orv synthetic plastic material, for instance a foam material or cellular material, the muffler 10 can accommodate itself to the contour of the outer surface of the housing portion 1, which may for instance be grooved or otherwise textured rather than smooth. This affords a particularly good sealing of the channels 14, 15 with respect to the ambient atmosphere at all points except where a communication is intended, namely through the openings 19. On the other hand, this type of sealing contact between the housing portion 1 and the muffler l0 prevents the transmission of resonance from the housing into the muffler 10.

The embodiment of FIG. 4 is analogous to that illus- I trated in FIGS. l-3, from which it differs in that air channels 21 and 22 are configurated differently. In all other respects the embodiment of FIGS. 1-3 is the same as that of FIG. 4, so that the latter need not be discussed in any greater detail, being self-evident.

It is'understood, of course, that the air channel could be configurated differently from what has been shown in FIGS. 1-3 on the one hand, and in FIG. 4 on the other hand, for instance depending upon the particular type of pneumatic tool with which the muffler is to be used. The muffler 10 itself may also be made as a shaped component of synthetic plastic material. It may be made in. its entirety of an elastically yieldable material, of for instance a cellular material of rubber or synthetic plastic. However, it is also possible to provide only the surface areas of the muffler 10 which come in contact with the housing portion 1 of the tool with an elastically yieldable material which can accommodate itself to the exterior surface contour of the housing portion l.v

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a pneumatic tool construction, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning andrange of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended:

1. In a pneumatic tool, a combination comprising a housing having an axis and including a curved portion having an external surface and provided with outlet openings for spent pneumatic fluid; and a muffler including a curved body dimensioned to embrace said curved portion and comprising a curved strip of sheet metal having an internal surface facing said external surface and defining therewith an annular clearance extending axially of said housing, and at least one shaped member of elastically yieldable' foamed synthetic plastic material located in said clearance and interposed between and in contact with said surfaces and defining therewith at least one enclosed tortuous channel for the passage of the spent fluid therethrough, said surfaces bounding said channel in the radially inward and outward directions, and said shaped member having first portions extending in said clearance at circumferentially spacedlocations in axial directionsofsaid housing, axially spaced curvedsectionportions connecting respective ends of said first portion's,'and' third portions extending intermediate said first portions away from the respective second portions towards but short of one another so as to define a gap between their adjacent ends, said channel having a first axial section provided with one end portion communicating with said outlet openings a second axial section having an other end portion spaced in circumferential direction of f said clearance from said one end portion,.and a circumferentially extending curved third section which extends through said gap and connects .said first and second section, said curved strip beingprovided in the region of said otherend portion with a plurality of "discharge apertures communicating said enclosed channel with the exterior of said muffler, whereby the spent fluid is restricted to movement in a tortuous path in said changap is located substantially midway between said second portions.

5. A combination as defined in claim 1, wherein said channel is configurated so as to cause a deflection of at least for the fluid issuing from said outlet openings into said channel. 

1. In a pneumatic tool, a combination comprising a housing having an axis and including a curved portion having an external surface and provided with outlet openings for spent pneumatic fluid; and a muffler including a curved body dimensioned to embrace said curved portion and comprising a curved strip of sheet metal having an internal surface facing said external surface and defining therewith an annular clearance extending axially of said housing, and at least one shaped member of elastically yieldable foamed synthetic plastic material located in said clearance and interposed between and in contact with said surfaces and defining therewith at least one enclosed tortuous channel for the passage of the spent fluid therethrough, said surfaces bounding said channel in the radially inward and outward directions, and said shaped member having first portions extending in said clearance at circumferentially spaced locations in axial directions of said housing, axially spaced curved section portions connecting respective ends of said first portions, and third portions extending intermediate said first portions away from the respective second portions towards but short of one another so as to define a gap between their adjacent ends, said channel having a first axial section provided with one end portion communicating with said outlet openings, a second axial section having an other end portion spaced in circumferential direction of said clearance from said one end portion, and a circumferentially extending curved third section which extends through said gap and connects said first and second section, said curved strip being provided in the region of said other end portion with a plurality of discharge apertures communicating said enclosed channel with the exterior of said muffler, whereby the spent fluid is restricted to movement in a tortuous path in said channel from said outlet openings through said first, third and second sections to said discharge openings.
 2. A combination as defined in claim 1, wherein said material is rubber.
 3. A combination as defined in claim 1, wherein said material is a cellular material.
 4. A combination as defined in claim 1, wherein said gap is located substantially midway between said second portions.
 5. A combination as defined in claim 1, wherein said channel is configurated so as to cause a deflection of at least 180* for the fluid issuing from said outlet openings into said channel. 